Horticulture CD
Unit 6-4: Nursery,
Landscaping, and
Gardening
Problem Area 6: Using and
Maintaining Tools and Equipment
Lesson 4: Maintaining Small
Engines
What Would You do if:
 Your lawn mower breaks down?
 Your weedeater won’t start?
 The engine on your shredder starts
to smoke?
Learning Objectives
 Describe equipment maintenance
schedules.
 Explain how to service intake/exhaust
and fuel systems.
 Discuss the maintenance of cooling and
lubrication systems.
 Discuss the servicing of compression
and ignition systems.
 Describe how to prepare equipment for
storage.
Terms
 Compression
Gauge
 Dry-type Air
Cleaner
 Dynamometer
 Fuel Strainer
 Hydrometer
 Long-term
Storage
 Maintenance
Interval
Terms Cont.
 Multi Meter (VoltOhm-Amp Meter)
 Oil Bath Type Air
Cleaner
 Oiled Foam Type
Air Cleaner
 Preventative
Maintenance
 Sediment Bowl
 Short-term
Storage
 Spark Tester
 Thumb Method
When Should Small Engine
Maintenance Jobs be
Performed?
 Describe equipment maintenance
schedules.
Small Engine Maintenance
 The two fundamentals for managing
small engines are to operate the
equipment as it was designed to be
operated and follow recommended
maintenance procedures.
Small Engine Maintenance
 Preventative maintenance is
performing periodic practices to
keep equipment in good working
order.
 By performing preventative
maintenance the owner tries to
prevent costly repairs and downtime.
Preventive Maintenance
 Clean air, fuel, and oil are keys to
maintenance.
 Changing fluids, cleaning components,
and replacing filters must be done on a
regular basis.
 Consult the engine operations manual or
service manual to develop a
maintenance schedule.
 Keep a written record of maintenance.
Preventive Maintenance
 Maintenance interval is the period
between service jobs measured in
either time (hours) or distance
(miles).
 Cars use miles, but tractors and
small engines use hours.
Preventive Maintenance
 Most manuals will divide maintenance
into intervals of:
 Daily before starting the engine, after the
first 5 hours, every 25 hours, every 50
hours, every 100 hours, and every 500
hours.
 These intervals are established for normal
operating conditions.
 If conditions are extremely dusty and dirty,
the intervals recommended in the manual
will be more often.
Maintenance Schedule
 Daily
 Check oil level and add oil as needed.
 Clean external surfaces of engine.
 Check for and tighten any loose bolts or
screws
 25 Hours
 Change crankcase oil.
 Service air cleaner.
 100 Hours
 Remove, clean, and re-gap the spark plug
or replace with a new plug.
How Can Clean Air and Fuel be
Ensured for the Engine?
 Explain how to service
intake/exhaust and fuel systems.
Cleaning the Air and Fuel Systems
 Fill the tank with clean fresh regular
grade gasoline that has been stored and
handled to properly.
 Fuel stored over 3 months deteriorates.
 Carburetor cleaner must be used to remove these deposits from a gas tank and
carburetor.
 Any rubber or plastic parts must be
removed before carburetor cleaner is used.
Cleaning Air and Fuel Systems
 Engines equipped with a sediment
bowl or fuel strainer should be
checked and cleaned according to
manufacturer’s recommendations.
 The sediment bowl is a glass or metal
bowl that allows particles (rust, metal,
etc.) and water to settle out of the fuel.
 A fuel strainer is a screen that keeps
particles from entering the carburetor.
Cleaning Air and Fuel Systems
 Carburetor adjustments vary with
the type of carburetor.
 Some small engines have factory
preset non-adjustable carburetors.
Air Cleaner
 To ensure clean air, the air cleaner
should always be in place and properly
serviced.
 A dry-type air cleaner contains no oil
and is usually made of a paper type
material.
 Cleaning involves tapping the element
against a solid surface.
 Elements that cannot be cleaned must
be replaced.
Air Cleaner
 The oiled foam type air cleaner uses
a piece of foam with an oil film to
attract dirt particles.
 Servicing involves cleaning the foam
in solvent or detergent followed by
drying and re-adding an oil film.
Air Cleaner
 The oil bath air cleaner uses a
fibrous element along with an oil
level to trap dirt particles.
 Servicing involves using solvent to
rinse the bowl and element and readding oil to the recommended
level.
Oiled Foam Air Cleaner
http://www.pecuniary.com/synthetics/airfilters.html
Fuel Filters and Air Cleaners
Cleaning Air and Fuel Systems
 Exhaust system maintenance
involves replacing the muffler as
needed.
 The muffler not only muffles noise but
also helps carry heat away from the
engine.
 Running an engine without a muffler is
not a good idea.
Muffler
http://members.tripod.com/~ks98/exhaust.htm
What Maintenance Does the
Cooling and Lubrication System
Need?
 Discuss the maintenance of cooling
and lubrication systems.
Cooling and Lubrication
 Cooling and lubrication are
secondary functions.
 Air-fuel mixture, compression, and
ignition (spark) are needed for any
engine to start and are called
primary functions.
 If the engine is to run for very long,
cooling and lubrication are essential.
Cooling
 Small engines are either air or liquid
cooled systems.
 The air system uses metal shrouds
and plates to help direct the air from
flywheel fins around the engine to
carry away the heat.
 Keeping the engine clean is the
most important service for this
cooling system.
Cooling
 Liquid cooled systems need to be
checked periodically for leaks and the
level needs to be monitored.
 A hydrometer is used to determine the
freeze protection level of the coolant by
measuring the specific gravity or density
of the coolant.
 Generally the coolant should be
approximately 50 percent anti-freeze
and 50 percent water.
Lubrication
 The lubrication system also helps carry
away heat and reduces friction, which
creates heat.
 If the lubrication system has an oil
pressure gauge, monitor the pressure.
 Check the oil level prior to starting the
engine.
 Follow oil change interval
recommendations.
 Use the oil recommended for the time of
year and conditions of use.
What Maintenance Needs to be
Done With the Compression and
Ignition
Systems?
 Discuss the servicing of
compression and ignition systems.
Compression System
 The purpose of the compression
system is to build up pressure in the
cylinder so that when the air-fuel
mixture is ignited the gases will
expand and generate power to drive
the piston down.
Compression System
 A compression gauge will measure
the compression in pounds per
square inch (PSI).
 The compression reading will give an
indication of the overall condition of
the engine.
Compression Systems
 The thumb method is a way of
testing compression by taking the
spark plug out and holding your
thumb over the spark plug hole.
 When the engine is cranked over, the
pressure should blow your thumb
away from the spark plug hole.
Compression Systems
 A dynamometer can be used to test
engine horsepower.
 As the compression of an engine
decreases with wear the horsepower
output of the engine goes down.
 After 500 hours of operation, it may
be recommended by the
manufacturer re-torque the cylinder
head bolts.
Dynamometer
http://www.dynomite.com/public/images/dyno/auto/engine/auto_engine_and_pro-2000_console_(600).jpg
Ignition System
 The purpose of the ignition system is to
provide the spark for a spark ignition
type internal combustion engine.
 Older style small engines still use a
mechanical type breaker point ignition
system.
 Breaker points and the condenser, along
with the spark plug are replaced.
Ignition Systems
 Modern engines use a solid state or
electronic ignition system.
 Solid-state ignition has greatly
decreased the amount of
preventative maintenance needed in
the ignition system.
Ignition Systems
 A spark tester placed between the
spark plug and the spark plug wire
will test the presence of a spark as
well as the strength of the spark.
Ignition Systems
 Keep the system clean.
 Check the condition of all wires and
connections.
 A multi meter (volt-ohm-amp meter)
can be used to check circuit continuity,
resistance, voltage, and amperage.
Ignition Systems
 For mechanical type ignition
systems, follow manufacturer’s
recommendations for adjusting the
point gap and replacing breaker
points and the condenser.
 In the solid-state systems, the control
module is often trouble-free for years.
 When the engine loses its spark, the
module will need to be replaced.
Ignition Systems
 With either system, clean, re-gap,
and re-install with a new gasket or
replace the spark plug at 100 hours
or once a year.
Ignition Systems
 If the engine has a battery ignition,
monitor the battery.
 Clean the surface by using baking soda to
neutralize the acid, keep the liquid level to
the line, and use a battery hydrometer to
test the state of charge.
 When the battery charge is low, use a
battery charger.
 Hook red to positive and black to negative.
What Should be Done to Prepare
an Engine for Storage?
 Describe how to prepare equipment
for storage.
Storage
 Storage can be short or long term.
 Short term storage is defined as
thirty days
 Long term storage is classified as
over thirty days.
Short Term Storage
 Engines in short term storage
should be stored in a dry inside
place or if outside covered with
plastic.
 Clean the engine, fill the fuel tank,
and shut off the fuel line.
 Service the air cleaner and change
the crankcase oil if necessary.
Long Term Storage
 Engines in long term storage need to be
cleaned and run until the fuel is burned.
 All filters should be serviced, the oil
changed, the spark plug serviced or
replaced, and the cylinder coated with
oil.
 Coat exposed or unpainted surfaces
with paint, grease or oil.
Long Term Storage
 If the engine is on a rotary
lawnmower, sharpen and balance
the blade.
 Store the engine in a clean dry
place covered with a waterproof
material such as plastic.
Review / Summary
 When should small engine maintenance jobs




be performed?
How can clean air and fuel be ensured for the
engine?
What maintenance does the cooling and
lubrication system need?
What maintenance needs to be done with the
compression and ignition systems?
What should be done to prepare an engine
for storage?